1. Field of the Invention
The present invention relates generally to avionics instrumentation and, more specifically, to retrofitting existing instruments and aircraft with electronic display-based instruments.
2. Description of the Related Art
Aircraft cockpit flight instrumentation (avionics) indicators may employ a variety of mechanisms, including vertical scale indicator mechanisms, radial dial indicator mechanisms, and pivoting mechanisms, such as those of compasses and attitude gyro indicators.
Many avionics indicators have long been entirely electro-mechanical, with needle pointers, rotating wheels, bands, spheres and so forth moving over or within a fixed dial or housing. For example, a vertical scale indicator that is used to indicate fuel flow commonly has an elongated rectangular housing, with a fuel flow scale printed numerically along its length, and a pointer band that moves lengthwise alongside the scale to indicate the current fuel flow. The instrument is mounted vertically on the cockpit instrumentation panel such that the pointer band appears to move or extend vertically. A pilot can thus determine at a glance that fuel flow is lower when the pointer band is shorter and higher when the pointer band is longer. A pilot can read the exact fuel flow by noting the point on the scale to which the pointer band extends.
Although fully solid-state display-based technologies, such as multi-function display instruments, have begun to supplant electro-mechanical indicators in commercial and military aircraft, general aviation (i.e., small private aircraft) pilots and regulatory authorities have been slower to accept such changes. General aviation pilots are generally accustomed to mechanical vertical scale indicators, radial dial indicators, attitude indicators and so forth. For example, in older CESSNA CITATION aircraft, electro-mechanical vertical scale indicators are used to indicate fuel flow, inter-turbine temperature, fan speed and turbine speed. It would be desirable to retrofit such older aircraft with solid-state electronic display-based instruments, but retrofitting with the latest multi-function display instruments is impractical and costly because their form factors differ greatly from those of the original instruments, and it can be difficult to obtain approval from regulatory authorities.
Accordingly, it can be seen that a need yet exists for a method and apparatus to replace existing electro-mechanical avionics display instruments, while allowing the replacement instrument to be fitted within the existing openings of the aircraft. It is to the provision of such a method and apparatus that the present invention is primarily directed.